I have been down the path you are on now. If I was doing it again I would pull the fuse box apart clean and check all the wires going to it. There are multiple wires in the fuel pump circuit. I found shorts in 4 or more wires.
This is the 88 electrical manual. I would save it so it's easily accessible. I even printed it all out. You going to need a decent multimeter, time, and patience.
The PO had installed this switch to $#!& of the fuel pump. I drive it that way while I fixed the rats nest of wiring.